Researchers find the organization of the human brain to be nearly ideal

July 6, 2015

A new strategy for mapping networks, from those underlying the Internet to the human brain, suggests possibilities for repairing damaged connections and disrupting dangerous ones. Credit: iStock

Have you ever wondered why the human brain evolved the way it did?

A new study by Northeastern physicist Dmitri Krioukov and his colleagues suggests an answer: to expedite the transfer of information from one brain region to another, enabling us to operate at peak capacity.

The paper, published in the July 3 issue of Nature Communications, reveals that the structure of the human brain has an almost ideal network of connections—the links that permit information to travel from, say, the auditory cortex (responsible for hearing) to the motor cortex (responsible for movement) so we can do everything from raise our hand in class in response to a question to rock out to the beat of The 1975.

The findings represent more than a confirmation of our evolutionary progress. They could have important implications for pinpointing the cause of neurological disorders and eventually developing therapies to treat them.

"An optimal network in the brain would have the smallest number of connections possible, to minimize cost, and at the same time it would have maximum navigability—that is, the most direct pathways for routing signals from any possible source to any possible destination," says Krioukov. It's a balance, he explains, raising and lowering his hands to indicate a scale. The study presents a new strategy to find the connections that achieve that balance or, as he puts it, "the sweet spot."

Krioukov, an associate professor in the Department of Physics, studies networks, from those related to massive Internet datasets to those defining our brains. In the new research, he and his co-authors used sophisticated statistical analyses based on Nobel laureate John Nash's contributions to game theory to construct a map of an idealized brain network—one that optimized the transfer of information. They then compared the idealized map of the brain to a map of the brain's real network and asked the question "How close are the two?"

Krioukov and his colleagues discovered that the structure of the human brain has an almost ideal network of connections (magenta), enabling optimal transmission of information from one part of the brain to another.

Remarkably so. They were surprised to learn that 89 percent of the connections in the idealized brain network showed up in the real brain network as well. "That means the brain was evolutionarily designed to be very, very close to what our algorithm shows," says Krioukov.

The scientists' strategy bucks tradition: It lets function—in this case, navigability—drive the structure of the idealized network, thereby showing which links are essential for optimal navigation. Most researchers in the field, says Krioukov, build models of the real network first, and only then address function, an approach that does not highlight the most crucial links.

The new strategy is also transferable to a variety of disciplines. The study, whose co-authors are at the Budapest University of Technology and Economics, mapped six diverse navigable networks in total, including that of the Internet, U.S. airports, and Hungarian roads. The Hungarian road network, for example, gave travelers the "luxury to go on a road trip without a map," the authors wrote.

Future applications of the research cross disciplines, too. Knowing what links in a network are the most critical for navigation tells you where to focus protective measures, whether the site is the Internet, roadways, train routes, or flight patterns. "Conversely, if you're a good guy facing a terrorist network, you know what links to attack first," says Krioukov. A systems designer could locate the missing connections necessary to maximize the navigability of a computer network and add them.

In the brain, the links existing in the idealized network are likely those required for normal brain function, says Krioukov. He points to a maze of magenta and turquoise tangles coursing through a brain illustration in his paper and traces the magenta trail, which is present in both the ideal and real brains. "So we suspect that they are the primary candidates to look at if some disease develops—to see if they are damaged or broken." Looking to the future, he speculates that once such links are identified, new drugs or surgical techniques could perhaps be developed to target them and repair, or circumvent, the damage.

"At the end of the day, what we are trying to do is to fix the diseased network so that it can resume its normal function," says Krioukov.

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Ideal doesn't necessarily mean "perfect". When in physics you say "ideal gas", you don't mean the best kind of gas, but one that behaves according to certain mathematical assumptions. It's the archetype of what a gas is like, rather than what gasses are supposed to be like.

If then, you find a substance that behaves accordingly, you can identify it as a gas because it resembles the idea of a gas. In the same way, if the real brain structure resembles the ideal of a certain kind of transmission network, you can make certain inferences about what the brain is doing and being.

"ideal" is junk. If my brain were even close to "ideal" , I would be 1,000,000 times smarter. And you can easily see I am not. One is not even close to the brain if you summulate the brain with say 1.000,000 conections. And the diagram above doesn't show 1000.

"ideal" is junk. If my brain were even close to "ideal" , I would be 1,000,000 times smarter.

You always have to ask "ideal for what". Our brains are evolved for "find food, find mate, don't get eaten by predators" - we've just repurposed this for a bunch of other things (like solving differential equations)

Teleology means basically to explain something based on some percieved purpose. The brains have no purpose and therefore they don't provide any specific functionality. They simply are.

What the brains are depends on what kind of brains can be. The ideal brain is exactly what exists, because it exists, because it needs not be anything else to exist. It wouldn't exist more if it were different in some respect.

Whether these brains then follow any other ideals such as energy efficiency, and to what extent, depends on how much they need to.

Teleology means basically to explain something based on some percieved purpose. The brains have no purpose and therefore they don't provide any specific functionality. They simply are.

That makes no sense. If a brain had no functionality then - during its evolution - any member of the species that had none would have had a vast evolutionary advantage (as all the food/energy needed by the 'brainy' one for the construction and upkeep could have gone to better uses - like mating earlier and more often). It would have gone the way of all traits that aren't of any benefit - that of the dodo. And being such an energy intensive organ it would have done so very, very fast.

Brains do not evolve. All cell type differentiation in all cells of all tissues of all organs and all organ systems is nutrient-dependent.

The honeybee model organism links nutrient-dependent pheromone-controlled brain development to the development of the human brain via the conserved molecular mechanisms of biophysically constrained protein folding chemistry.

Some don't seem to. You are a prime candidate of that.In truth though even yours is a step in evolution. Unfortunately your genetics mutation from the mixture of your parents genes led to your developing the extreme mental illness you show so regularly everywhere you post. Is that why you really hate evolution and mutations and refuse to change your beliefs even when proven wrong so much?

@jkso, you are saying that this brain, in all it's glory, sprang immediately from nothing suddeny?out of what? - a penchant for peanuts? or was it sugar, which feeds it?

if we have brains which are "an ecological adaptation" based upon our diet, why did it spring forth into what we have today and not simply stay the same as a chimp or orangutan, or something similar?Why not even a hummingbird?

Just because you want to obfuscate biological processes and create word-salads with techno-jargon doesn't mean you comprehend biology: to date, you have epically FAILED to interpret a single study where the authors have given feedback on your "interpretations" of their work.

that kind of failure suggest: Dunning-Kruger, Narcissism, mental illness and a lot more (See JSDark above)

Basically, to say that brains have evolved to "find food and avoid predators at minimum energy cost" is to give a teleological purpose for evolution - as if it was seeking a goal set by some other entity.

Imagine you had a conveyor belt, and along the belt there are different shaped gates much like in the game show "Hole in the Wall", and you place inanimate objects on the belt and see what comes out the other end. The objects tumble down through the gates along the belt, and at the end you see one that wasn't caught.

Do you say that the reason it got there was because that was its purpose, or because it just happened to tumble the right way?

Similiarily, every living evolving being is on a random trajectory through the space of possible trait combinations, being knocked off the belt where they can't fit through, so brains aren't energy efficient because they need to be, but because other kinds of brains can't be.

This is not surprising, the cortex that is tied together by more basal tissue is old - both vertebrates ("cortex") and invertebrates ("mushroom bodies") have orthologs.

@Eikka: Populations have evolved so that brains have a function. Of course the process has no telepatic, teleportation 'teleology' (comprehensive foresight). On the other hand brains are "supposed" to be there by the current organisms, their genes control for brain development in their current environment, and without it the organisms fail to procreate.

Evolution is not a "random" trajectory, selection is largely deterministic, it is a contingent trajectory (depends on stochastic variation and environment). Also, not all organism traits are selected for (spandrels) or 'best' (positive and negative selection; recent changes).

Excerpt: It has become obvious to many serious scientists that microRNAs control the development of the body and the brain in insect species and in mammals. Control appears to involve the finely tuned balance of viral microRNAs and nutrient-dependent microRNAs.

Plants were created first! Viruses appear to have begun to perturb protein folding in microbes, plants, and animals after the de novo creation of light-induced amino acids, which links them to RNA-mediated cell type differentiation in all cells of all individuals of all genera via their biophysically constrained chemistry of nutrient-dependent protein folding and physiology of their reproduction.

"...nearly half of the 50 chicken meat samples purchased from supermarkets, street markets, and butchers in Austria contained viruses that are capable of transferring antibiotic resistance genes from one bacterium to another—or from one species to another."

In Lenski's experiment, when the translocation occurred resulting in the oxic cit+ trait, the resulting strain had better access to nutrients. Because of that, they could outgrow the ancestral strain. They became better and outcompeted. That's just one example of selection. If I described it and called it anything else besides selection, you wouldn't have a problem with it, but you have some arbitrary aversion to that word as well as "evolve".

If I described it and called it anything else besides selection, you wouldn't have a problem with it, but you have some arbitrary aversion to that word as well as "evolve".

Obviously, you must separate selection from evolution because you can't link what was selected to when it was selected and get to evolution. But, even if you ever link the two, they have already been separated by Nei in his textbook "Mutation-Driven Evolution."

Excerpt: "...genomic conservation and constraint-breaking mutation is the ultimate source of all biological innovations and the enormous amount of biodiversity in this world. In this view of evolution there is no need of considering teleological elements" (p. 199).

Simply put, he claims that evolution 'just happens,' not that it happens via selection. Thus, it seems you have invented your own theory, but won't tell anyone what it is.

When the food runs out but sunlight is abundant, then photosynthesis works better" to support an organism, Bhattacharya notes. And from that forced union a supergroup of extremely successful organisms—the plants—sprang.

From the dawn of creation, the light-induced de novo creation of amino acid substitutions -- via the speed of light being slowed on contact with water -- led to the RNA-mediated amino acid substitutions that differentiate all nutrient-dependent cell types in all individuals of all living genera.

"...—the plants—sprang" is akin to saying that evolution "just happens."

2- you have never once been able to produce empirical evidence other than "because jk said so" that links the speed of light to the de novo creation of amino acids, let alone to link it causative to "the RNA-mediated amino acid substitutions"

3- pseudoscience claims without evidence can be dismissed as creationist religious horse-puckey as there is so substance to claims without evidence

Then, fix yourself a salad or join others who are Combating Evolution to Fight Disease.

See also: http://medicalxpr...ted.html"... Our results show that patients who suffer from mycobacterial infections as a result of RORC mutations can be treated with interferon-γ—a potentially life-saving intervention," Casanova says. "By finding that RORC helps control the development of these two cytokines, interleukin-17 and interferon-γ, we have revealed a surprisingly dual role for RORC in human immunity to infection."

your "link" does not, in ANY way, link "the speed of light on contact with water to the de novo creation of amino acids"!ROTFLMFAO

what it *does* do is suggest that

all the cellular subsystems could have arisen simultaneously through common chemistry. The key reaction steps are driven by ultraviolet light, use ​hydrogen sulfide as the reductant and can be accelerated by Cu(I)–Cu(II) photoredox cycling.

IOW - you are promoting Evolution and it's theory, you know that?

it also suggests

we experimentally investigate the validity of this assumption by examining the assembly of various biomolecular building blocks from prebiotically plausible intermediates and one-carbon feedstock molecules. We show that precursors of ribonucleotides, amino acids and lipids can all be derived by the reductive homologation of ​hydrogen cyanide and some of its derivatives

your "link" does not, in ANY way, link "the speed of light on contact with water to the de novo creation of amino acids"!

Is there any other science idiot who doesn't know how photosynthesis occurs?

all the cellular subsystems could have arisen simultaneously through common chemistry.

Is there any other science idiot who does not understand the link from photosynthesis to plant and animal life occurs in the context of their nutrient-dependent biophysically constrained chemistry of protein folding and the physiology of their reproduction?

http://dx.doi.org...2013_499 "Laboratory experiments have shown that the UV photo-irradiation of low-temperature ices of astrophysical interest leads to the formation of organic molecules, including molecules important for biology such as amino acids..."

Excerpt: "...an alternative way to compensate for gene loss is to move genes from the degraded Y chromosome to other, non-sex chromosome locations..."

The inventors of neo-Darwinism are wrong. There are no "lower races" and sex differences in cell types didn't evolve.

Cell type differentiation is nutrient-dependent and controlled by the physiology of reproduction in all living genera. Experimental evidence links chromosomal rearrangements to biodiversity instead of mutations. Biologically uninformed science idiots like PZ Myers don't like that fact.

I have detailed the link from the light-induced de novo creation of amino acids to cell type differentiation via RNA-mediated amino acid substitutions in all genera. It is clear that chromosomal rearrangements are the source of biodiversity that biologically uninformed science idiots like PZ Myers teach others is due to mutations and evolution.

The best that other biologically uninformed science idiots can do is try to put words in my mouth.

you are saying that photosynthesis is the DE NOVO creation of amino acids by the speed of light impacting with water?

What I've said is contained in a series of published works, and this invited review of nutritional epigenetics.

Excerpt from my invited review: "The ability of nutrients to epigenetically effect changes in base pairs and to alter the miRNA/mRNA balance appears to link food odors; cell type-specific alternative splicings of pre-mRNA; de novo gene creation and pseudogene creation; chromosomal rearrangements and the metabolism of nutrients to species-specific pheromones that control the physiology of reproduction in species from microbes to man (Diamond, et al., 1996; J. V. Kohl, et al., 2001) (J. V. Kohl, 2012, 2013). The bottom-up epigenetic effects of food odors associated with nutrients and the top-down epigenetic effects of pheromones seem to act within the context of biophysically constrained conserved molecular mechanisms that finely tune the transcriptional output of different alleles."

DNA methylation and single nucleotide variants in the brain-derived neurotrophic factor (BDNF) and oxytocin receptor (OXTR) genes are associated with anxiety/depression in older womenhttp://www.fronti...15.00230

The obvious effect on hormones that affect behavior via a single base pair change and one amino acid substitution during the life history transitions of humans (that can be linked to hormone changes with menopause) is:

Since 1985, the fact that chromosomal rearrangements are the source of all biodiversity has been linked from viruses to all extant biodiversity via the anti-entropic epigenetic effects of nutrient-dependent microRNAs on RNA-mediated gene duplication, which is controlled by fixation of amino acid substitutions in the context of the physiology of reproduction in all genera. In species from microbes to man, pheromones control nutrient-dependent RNA-mediated gene duplication via the physiology of reproduction.

In all cases, at least one of the two DSBs is generated by a pathologic process, such as (1) randomly-positioned breaks due to ionizing radiation, free radical oxidative damage, or spontaneous hydrolysis; (2) breaks associated with topoisomerase inhibitor treatment; or (3) breaks at direct or inverted repeat sequences, mediated by unidentified strand breakage mechanisms.